Legionnaires' Disease and Pontiac Fever (Legionellosis)

  • Medical Author:
    George Schiffman, MD, FCCP

    Dr. Schiffman received his B.S. degree with High Honors in biology from Hobart College in 1976. He then moved to Chicago where he studied biochemistry at the University of Illinois, Chicago Circle. He attended Rush Medical College where he received his M.D. degree in 1982 and was elected to the Alpha Omega Alpha Medical Honor Society. He completed his Internal Medicine internship and residency at the University of California, Irvine.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Bacterial Infections 101 Pictures Slideshow

How common is Legionnaires' disease?

Legionnaires' pneumonia is not uncommon. In fact, it represents over 4% of all community-acquired pneumonias. An additional unknown number of people are infected with the Legionella bacterium but have only mild symptoms or no symptoms at all (so-called Pontiac fever).

Outbreaks of Legionnaires' disease have received the most media attention. A recent outbreak was associated with a party at the Playboy mansion in Los Angeles where at least four individuals contracted Legionnaires' disease. However, the disease most often occurs as single, isolated cases not associated with any identified outbreak. Outbreaks are usually recognized in the summer and early fall, but cases may occur year-round.

Since the bacterium of Legionnaires' disease was identified in 1976, numerous hospital-acquired outbreaks of the disease have also been reported. These outbreaks have enabled researchers to study epidemics of legionellosis.

What are the usual symptoms of Legionnaires' disease?

Patients with Legionnaires' disease usually develop a fever, chills, and a cough. The cough may either be dry or produce sputum. Some patients with Legionnaires' disease also have muscle aches, headache, tiredness, loss of appetite, and occasionally diarrhea. Legionnaires' disease can cause a severe pneumonia, seriously affect breathing, even lead to respiratory failure and adult respiratory distress syndrome (ARDS). In some cases, the heart rate is slower than expected for the degree of fever. There are no specific symptoms that directly identify Legionnaires' pneumonia. Legionnaires' pneumonia presents in a manner similar to Chlamydia pneumonia and Mycoplasma pneumonia, so-called atypical pneumonias (previously referred to as "walking pneumonia"). These are referred to as atypical because the associated symptoms and signs are unlike typical pneumonia (as characterized by Streptococcus pneumonia), which involves high, spiking fevers, sudden onset, cough, and purulent sputum and often chest pain and a localized infiltrate on chest X-ray.

People with Pontiac fever experience a self-limiting influenza-like illness with fever, chills, headache, and muscle aches but, by definition, do not have pneumonia. Affected individuals generally recover in two to five days without treatment.

Medically Reviewed by a Doctor on 3/23/2016

Subscribe to MedicineNet's Newsletters

Get the latest health and medical information delivered direct to your inbox!

By clicking Submit, I agree to the MedicineNet's Terms & Conditions & Privacy Policy and understand that I may opt out of MedicineNet's subscriptions at any time.

VIEW PATIENT COMMENTS
  • Legionnaires' Disease - Causes

    How did you or someone you know contract Legionnaires' disease? Please share your experience.

    Post View 3 Comments
  • Legionnaires' Disease - Symptoms

    What were the symptoms associated with Legionnaires' disease in you, a friend, or relative?

    Post View 4 Comments
  • Legionnaires' Disease - Diagnosis

    What were the events, tests, or exams that led to a diagnosis of Legionnaires' disease?

    Post
  • Legionnaires' Disease - Treatment

    What kinds of treatment, including medication, did you or someone you know receive for Legionnaires' disease?

    Post

Health Solutions From Our Sponsors